1. Field of the Invention
The present invention relates to a method of processing spectral data in two-dimensional representation. The method gives accurate feature information about an analyzed object by applying differential operations to the processing of spectral data of the analyzed object in spectroscopic analysis. The present invention also relates to a method of correcting spectral data. The method equalizes or corrects the reference values or baselines for determination for the spectral data by the above processing method. The spectroscopic analysis includes Infrared, near-infrared, visible, or ultraviolet spectroscopic analysis, various chromatogram analysis, Raman spectroscopic analysis, electron ray or X-ray spectroscopic analysis, and the like.
2. Description of the Related Art
In general, spectroscopic analysis, for example, infrared absorbance spectroscopic analysis, measures the intensity spectrum of light transmitted through or absorbed by an object for analysis, called analyzed object hereafter, and obtains various scientific features or information, called feature information hereafter, about the analyzed object, based on the spectral form or spectral profile. As the spectral form, the absorbance for analyzed object expressed as a function of the wavenumber or wavelength, called absorbance-wavenumber spectral profile hereafter, has been widely used.
However, such conventional spectroscopic techniques that obtain various feature information based on the absorbance-wavenumber profile cannot accurately extract all feature information, although a great number of features are contained in spectral data. Therefore, there have been problems that the techniques cannot obtain much feature information about the analyzed object, and the accuracy is not much great, depending on the obtained feature information. Therefore, a processing technique or analytical technique for, spectral data is desired in order to obtain more feature information with greater accuracy.
Further, quantitative spectroscopic analysis requires the creation of a number of standard samples and the creation of a quantitative model from the spectral data of the standard samples. In this case, the spectral data of each standard sample is obtained by individual spectrometry. Measuring conditions, such as the conditions of the spectrometer and conditions of samples, in spectrometry vary, no matter how much care is taken. Therefore, the spectral data of standard samples contain deviations or errors due to such fluctuations in measuring conditions.
Specifically, there exists a base section that is non-effective for obtaining feature information, in an absorbance-wavenumber profile obtained from such spectral data. The boarder between the effective section for obtaining feature information and the non-effective section is called the reference (reference for determination) or baseline. The reference for determination or the baseline fluctuates with the drift of the spectrometer and the conditions of the sample. Therefore, in order to create a quantitative model from the absorbance-wavenumber profiles of standard samples, it is necessary to equalize or correct the references for determination or the baselines of the spectral profiles of the standard samples.
However, it is difficult for conventional spectroscopic techniques that uses absorbance-wavenumber spectral profiles to equalize or correct the references for determination or the baselines. In particular, if the standard samples are aqueous solutions, it is impossible to determine the baseline in an absorbance-wavenumber profile, so that the creation of the reference for determination or the baseline and the creation of a quantitative model is extremely difficult.